Regenerated cellulose fibrous product

ABSTRACT

A FIBROUS PRODUCT COMPRISING A LARGE NUMBER OF REGENERATED CELLULOSE FIBRIL-LIKE MICROFIBERS HAVING A DIAMETER OF 0.1 TO 5U. AT LEAST A PORTION OF SAID FIBRIL-LIKE MICROFIBRES BEING MUTUALLY ENTRANGLED. THE FIBROUS PRODUCT, AHVING A HIGH WATER-RETAINING PROPERTY AND A HIGH APPARENT DEGREE OF SWELLING, IS OBTAINED BY INTRODUCING A VISCOSE SPINING DOPE INTO A COAGULATION LIQUID, WHEREIN A REDUCED PRESSURE GENERATED BY THE HIGH SPEED FLOW OF SAID COAGULATION LIQUID IS EMPOLYED TO APPLY A SHEAR STRESS TO THE SPINNING DOPE.

Jam. 15, 17% ATSUSH] KAWAl ET AL RBGENERATED CELLULOSE FTBHOUS PRODUCT Filed Oct. 20, 1970 5 Sheets-Sheet 1 Jan. 15, 1974 ATSUSHI KAWAI ETAL 3,785,913

REGENERATED CELLULOSE FIBROUS PRODUCT 5 Sheets-Sheet 2 Filed Oct. 20, 1970 FIG. 2

ATSUSHI KAWAI ET AL REGENBRATED CELLULOSFJ PIBROUS PRODUCT Filed Oct. 20, 1970 5 Sheets-Swat 1* INVENTOR'5 A'TSUSHI KAN/1H, MlG-AKU SUZL)k\ AND Hmamom OHTA BY CY'OKB AfltoneLLL Stewart ATTORNEYS y H74 ATSUSHI KAWAI ET AL REGENERATED CELLULOSE PTBROUS PRODUCT Filed Oct. 20, 1970 5 Sheets-Sheet 5 TEMPE/247w? c) 8 W W1 l INVENTORS ATSUSHL KAbJ H, mar-mu zm AND H (buxom ou-rfi BY Craig, Antmm, 5% w M ATTORNEY United States Patent 3,785,918 REGENERATED CELLULOSE FIBROUS PRODUCT Atsushi Kawai, Migaku Suzuki, and Hidenori Ohta, Ohtake, Japan, assignors to Mitsubishi Rayon (30., Ltd., Tokyo, Japan Filed Oct. 20, 1970, Ser. No. 82,276 Claims priority, application Japan, Oct. 24, 1969, 44/854162 Int. Cl. B321) 5/02, 5/16 US. Cl. 161-169 9 Claims ABSTRACT OF THE DISCLOSURE A fibrous product comprising a large number of regenerated cellulose fibril-like microfibers having a diameter of 0.1 to in, at least a portion of said fibril-like microfibers being mutually entangled. The fibrous product, having a high water-retaining property and a high apparent degree of swelling, is obtained by introducing a viscose spinning dope into a coagulation liquid, wherein a reduced pressure generated by the high speed flow of said coagulation liquid is employed to apply a shear stress to the spinning dope.

The present invention relates to a novel fibrous product comprising a large number of regenerated cellulose fibril-like microfibers and to a process for producing and using the same with industrial advantages.

Heretofore, paper has been produced by subjecting v natural cellulose fibers to beating to defibrate, cut, swell, fibrilate and broaden the surface area of the fibers,

thereby making possible the mutual adhesion of fibrils at the paper-making step to form a sheet. Hence, when subjected to beating, a natural cellulose fiber is transformed into fibrils capable of being adhered to one another.

In order to impart to the fiber the type of mutual adhesion seem in wood pulp fibers, it is necessary that the fiber should be provided with the same defibrating, cutting, swelling and fibrillating properties as in the case of wood fiber. For this reason, attempts have been made, in the production of self-adherable regenerated cellulose fibers having self-bonding property, to make the fibers hollow so as to have a thin fiber wall, to make the fibers fiat in cross-section or to treat the fibers with a swelling agent.

f One of the objects of the present invention is to provide a novel fibrous product comprising a large number of regenerated cellulose fibril-like microfibers which has a high water-retaining property and a high apparent degree of swelling.

Another object of the invention is to provide a process for producing said fibrous product which may be carried and claims, taken in conjunction with the accompanying drawings and wherein:

FIG. 1 shows several sketches of composite fibrous products obtained according to the present invention in which (1) indicates the case where a cut fiber piece (b) has been covered with the fibril-like regenerated cellulose microfibers (a) of the present invention, (2) indicates thecase where a flake-like material (b) has been covered with the fibril-like regenerated cellulose micro- "ice fibers (a), (3) indicates the case where an inorganic powder (b) has been covered with the fibril-like regenerated cellulose microfibers (a), and (4) indicates the case where a fibrillar fiber (b) of a synthetic polymer has been used in combination with the fibril-like regenerated cellulose microfibers (a);

FIG. 2 is a photomicrograph, enlarged 300 times, of a fibrous product obtained in accordance with the present invention;

FIG. 3 is a longitudinal section of the aspirator portion of the aspirator-type spinning apparatus used in the present invention, wherein 1 is an inlet for the coagulation liquid, 2 is an inlet for the spinning dope and 3 is an outlet for the mixture;

FIG. 4 shows an example of a process diagram, wherein 4 is a pump, 5 is an ejector, 6 is a viscose tank and 7 is a coagulation liquor tank;

FIG. 5 is an example of a procedure flow sheet in accordance with the present invention;

FIG. 6 is a graph showing the increase of temperature with time of various cooled materials; and

FIG. 7 is a graph showing the decrease of temperature with time of various heated materials.

In accordance with the present invention and as the result of our extensive studies on techniques for fibrillating regenerated cellulose fibers, it has been found that a regenerated cellulose fibril-like microfiber having high water-retaining ability and high apparent swelling ability can be obtained by the adoption of a specific spinning process.

Because of its extremely high fibrillar structure, the fibrous product of the present invention has entangling and felting actions such as that of a beaten natural cellulose fiber. The characteristics thereof are enumerated below.

(1) The fibrous product of the present invention is composed of a large number of regenerated cellulose fibril-like microfibers of 0.1 to 5 in diameter, and at least a portion of said microfibers being mutually entangled one with another. Hence, it may be said that the fibrous product of the present invention is not a single fiber which has been fibrillated but is an aggregate of microfibers. According to the present invention, a fibrous product having an apparent fiber length of from about 1 mm. to about 30 mm. may be obtained by sui ably selecting the production conditions.

(2) The fibrous product of the present invention is extremely high in water-retaining ability, and a water retaining ratio of about 500 to about 4,000% can be attained by a suitable selection of conditions. The water retention ratio referred to in the above is a value calculated according to the following equation:

X (percent) X 100 (percent) wherein D is the dry weight of the fibrous product and W is the wet weight thereof after it has been immersed for 1 hour in distilled water at 20 C. and then centrifuged at 1,000 G for 10 minutes.

(4) An aqueous dispersion of the present fibrous product is markedly stable and takes an extremely long period of time incompletin'g agglomeration and precipitation.

(5) According to the so-called TAPPI method, the fibrous product of the present invention shows a Canadian freeness of less than 80, and when highly fibrillated, it shows a value of substantially 0.

(6) The fibrous product of the present invention is extremely low in degree of crystallization and is similar in properties to non-crystalline cellulose. When subjected to X-ray diffractiometry, the present fibrous product shows a crystallization degree of less than 20%.

When the present fibrous product, which has the characteristics as mentioned above, is dispersed into an aqueous dispersion and is then subjected to a paper-making operation, a transparent paper having very little air permeability, like parchment paper, is obtained. When used in admixture with other fiber materials, metals or plastics, the present fibrous product shows a strong binding effect. Further, when sufficiently dried according to a solvent substitution method or the like, the present fibrous product can be utilized as an extremely strong water absorbent.

The above-mentioned characteristics are considered ascribable to the fibrillar structure of the fibrous product of the present invention and to the synergistic action of the fibrillar structure with the water swellability derived from the non-crystalline structure thereof. By utilization of these characteristics, many applications of the present fibrous product are practical, as will be mentioned later.

In order to produce the fibrous product of the present invention, it is necessary to select suitable conditions for generation of the fibrillar structure. In order to form said fibril-like microfibers, it is essential that a fiber-forming polymer be elongated so as to arrange the molecules in parallel to one another prior to completion of the coagulation of the polymer. Accordingly, it is necessary that the arrangement of the molecules be effected at a stage where the energy of intermolecular action is extremely low, i.e., at the most initial stage of spinning. For this purpose, it has been found to be effective to keep the coagulation rate relatively low by suitably controlling the conditions of the spinning dope (spinning solution) and of the coagulation liquid.

In order to form fibril-like microfibers at the most initial stage of spinning, it is necessary that the spinning dope be coagulated while applying a shear stress thereto. For this purpose, there may be adopted any of the conventional procedures, such as the viscose spinning process, flow tube-type spinning process, stirring type-spinning process and spraying type-spinning process. Particularly, however, it is ideal to adopt an aspirator type-spinning process in which a coagulation liquid is flowed at a high speed and a spinning dope is introduced by the utilization of a reduced pressure generated by virtue of the high speed flow of the coagulation liquid. According to this process, a strong shear stress is applied at the most initial stage of spinning to a fiber-forming material to arrange and coagulate the molecules thereof, thereby giving the fibril-like microfibers.

Preferred embodiments of the spinning dope, coagulation liquid and spinning apparatus to be used in the present invention are explained below.

(1) Spinning dope: An alkali solution of sodium cellulose xanthate, i.e., a so-called viscose, is used as a suitable and effective spinning dope in the present invention. In some cases, however, a cuprammonium solution of cellulose may also be used. It is desirable that the spinning dope contain 0.5 to 9% by weight of cellulose and 0.2 to 7% by weight of alkali and have a viscosity of 1 to 80 poises and a 'y-value of at least 20. The spinning dope may be incorporated with a solution, emulsion or suspension of various additives, e.g., various cut fibers, various rubber latexes, mineral powders, water-soluble polymers such as polyvinyl alcohol or polyacrylic acid amides. In

order to disperse additives in the form of solids or suspensions, the addition of surfactants is effective Thealkali cellulose used or a viscose prepared therefrom may or may not be subjected to aging, filtration or defoaming.

(2) Coagulation liquid: The coagulation liquid used in the present invention should be a liquid which can coagulate the viscose spinning dope employed and-which is suitable for producing the fibril-like microfibers described herein. Examples of such coagulation liquids are aqueous acid solutions, formaldehyde-containing aqueous acidic solutions, hydrophilic solvent-containing aqueous solutions and mixtures thereof.

As the aqueous acidic solution, aqueous solutions containing sulfuric acid are used, in general. The solution may further contain sodium sulfate and zinc sulfate. Preferably, however, the sum of the sodium sulfate and zinc sulfate is less than 10%, and it is desirable that the solu tion contain only sulfuric acid. The concentration'of sulfuric acid is generally in the range of 0.5 to 18% by weight, preferably 2 to 12%. In case that the bath ratio (of the viscose/coagulation liquid) is definite, the weight (A/B) of the alkali concentration (A) in the spinning dope to the sulfuric acid concentration (B) in the coagulation liquid greatly affects the surface fibrillar state and the form of the resulting microfibers. In the case where the sulfuric acid concentration is 0.5% to 18% and the ratio A/B is outside the range of 0.04 to 3, resulting product becomes powdery and cannot maintain a microfiber state. Therefore, the ratio A/B should be maintained in a range of 0.04 to 3. In the case where the ratio A/B is lowered from 2 to 0.3, the development of the fibril-like structure becomes marked to give a fibrous product high in water retaining ability.

And when the ratio A/B is lowered from 0.1 to 0.05, the formation of the fibril-like structure is generally depressed and approaches a fine film-like structure, so that the fibrous-product is decreased in water retaining ability and is increased in apparent fineness of the microfibers. When formaldehyde is added to the coagulation liquid, the development of the fibril-like structure is promoted, the lfiJfiO A/B may be extended from 0.04 to 3, and the apparent fiber length of the microfibers is increased.

However, it is necessary that the amount of zinc sulfate or the like heavy metal compound to be added into the coagulation liquid should be less than 0.5% by weight. The concentration of sulfuric acid is desirably in the range of l to 18% by weight. The fonmaldehyde concentration in the coagulation liquid may be in the range of 0.5 to 20 g./l. The same effect as that obtained with formaldehyde can also be attained by the use of a Water soluble solvent having a dehydrating action, such as acetone, ethanol, methanol, propanol, tetrahydrofuran, dioxane, or the like, i.e., organic alcohol, ketones or ethers. When the viscose is added to a coagulation liquid containing such a solvent, an extremely high fibril-like structure is formed. In order to sufficiently display the solvent effect, the weight ratio S/ W of the solvent (S) to the water (W) should be more than 1.5, preferably more than 3.

The particular coagulation liquid employed varies, depending on the end uses of the resulting fibrous product. In the case where the fibrous product is to be used for such a purpose as to utilize water retainability and swellability derived from the fibril-like structure and noncrystalline structure thereof, the spinning dope is introduced into an aqueous sulfuric acid or aqueous formaldehydesulfuric acid solution to form the fibrous product and the product thus formed is subjected to a regeneration treatment and scouring treatments according to the conventional procedures. However, in the case where such properties as (1) the water solubility of the sodium cellulose xanthate remaining in the microfibers obtained by use of the coagulation liquid containing the solvent or (2) the solubility in a specific medium of the formaldehyde derivative of cellulose xanthate in the microfibers obtained by use of the coagulation liquid containing formaldehyde are to be utilized, in addition to the aforesaid properties, the fibrous product after spinning may be used as-it is without any further treatment. The fibrous product of the present invention may be utilized as a fiber binder for a non-woven fabric or the like. In that case, it is also possible to. impart to the fiber binder a melt-adhering property.

The type of coagulation liquid employed varies depending not only on the end uses of the resulting fibrous product as mentioned above, but also on the kind of spinning dope used. For example, in the case where thermal fusibility is desired to be imparted to the fibrous product by adding to the viscose a large amount of a rubber latex such as ethylene-vinyl acetate copolymer or the like, the use of an aqueous sulfuric acid solution as the coagulation liquid results in that the rubber particles are precipitated in the regenerated cellulose, so that the development of the fibril-like structure is greatly inhibited. If, in the above case, a solution containing a hydrophilic solvent high in dehydrating ability such as methanol, acetone or ethanol is used as the coagulation liquid, not only is the cellulose fibrillated, but also the rubber particles grow and precipitate in the form of fibrils to give a fibrous-product comprising a mixed fibril-like structure. This fibrous product is a composite of a hydrophilic material (regenerated cellulose) and a hydrophobic material (rubber substance) and is quite excellent in water dispersibility and high in binder efficiency as compared with the conventional rubber type fibrous binder.

The thus-obtained fibrous product is subjected to a conventional regeneration treatment using a high temperature bath to complete the regeneration. The regeneration treatment is desirably carried out at a temperature of 80 C. or above. Thereafter, the fibrous product is subjected to conventional scouring treatments such as bleaching, waterwashing and the like.

(3) Spinning apparatus: In a coagulation liquid containing formaldehyde and/or a solvent, fibrillation takes place with relative ease by mixing or stirring the spinning solution with the coagulation liquid. However, in the case where an aqueous sulfuric acid solution is used as the coagulation liquid, the state of fibrillation is delicately affected by the flow rate distribution of the coagulation liquid. For the continuous and uniform production of such a fibrous product, the process of the present invention is extremely advantageous.

The process employed in the present invention is carried out by the use of an ejector (aspirator) type-spinning apparatus comprising, as shown in FIG. 3, ('1) an inner tube for ejecting a coagulation liquid at a high flow rate and (2) an outer tube having an opening for introducing a spinning dope by utilizing reduced pressure generated by the flow of the coagulation liquid. According to the process of the present invention, a coagulation liquid is passed at a high speed throughout the inner tube (1) into the apparatus, a spinning dope controlled to a suitable viscosity is fed through the outer tube (2), and the coagulation liquid and the resulting microfibers are discharged at a high flow rate through a discharge pipe (3), whereby a strong shear stress is applied at the most initial stage of spinning to the fiber-forming material, and the fiber molecules in the spinning solution are arranged and coagulated to produce a highly fibrillated fiber. Ordinarily, the spinning dope is introduced by utilization of reduced pressure generated by ejecting the coagulation liquid through the inner tube (1). In some cases, however, the spinning dope may be introduced under pressure. For the formation of fibril-like microfi'bers, it is necessary that the fiber-forming material be elongated prior to coagulation to arrange the molecules thereof in parallel. It is therefore necessary that the arrangement of the fiber molecules should be effected at a state where the energy of molecular interaction is extremely small, i.e., at the most initial stage of spinning. The apparatus employed in the present invention characteristically satisfies the above-mentioned requirement.

Factors to be taken into consideration with respect to the spinning apparatus shown in FIG. 3 are the flow rate of the liquid at the narrowed portion of the aspirator, the diameter (a) of the narrowed portion of the aspirator, the extent of insertion (b) of the inner tube into the narrowed portion, the length (0) of the narrowed portion, the angle (0) of the narrowed portion to the portion where the flow rate is lowered, and the diameter (d) of the portion where the flow rate is lowered. If the flow rate of the liquid at the narrowed portion of the aspirator is excessively low, the fiber-forming polymer is brought into the form of agglomerates or strands, and if the flow rate is excessively high, the fiber-forming polymer is brought into the form of a powder. Accordingly, the flow rate of the coagulation liquid at the narrowed portion of the spinning apparatus is 70* to 3,000 m./min., preferably 200 to 1,500 m./min. The diameter (a) of the narrowed portion is at least 0.5 mm., preferably at least 2.0 mm. The degree of insertion (b) of the inner tube into the narrowed portion is at least 0.2 mm., preferably at least 1.0 mm., whereby the narrowed portion is greatly prevented from the danger of clogging by the resulting fibrous product. The length (0) of the narrowed portion is desirably at least 2X (a). The angle (0) of the narrowed portion to the portion where the flow rate of the liquid is lowered is less than preferably less than 45. If the said angle is excessively great, the liquid How is disturbed at the portion Where the diameter is enlarged to form knotty fibers, whereby the dispersibility thereof and the uniformity of the final product are injured. The diameter of the portion at which the flow rate is lowered is desirably in the range of 2 (a) to 50X (a). 1

By use of the above-mentioned apparatus, advantages such as those mentioned below can be attained.

1) Unlike the conventional spinneret, it is not required that the nozzle diameter be made small. Accordingly, no filtration or defoaming of the spinning dope is necessary, and thus the production steps can be simpli fied to a great extent. In some cases, the fibrillation is promoted by the use of a large amount of fine air bubbles or a foaming agent.

(2) A solid organic or inorganic material may be dispersed in either one or both the spinning dope and the coagulation liquid, whereby the dispersed material is bonded and coated with the regenerated cellulose, while the spinning dope is coagulated into the form of fiber by contact with the coagulation liquor, making it possible to obtain a composite fibrous product. As the material to be dispersed, natural or synthetic cut fibers, powders of inorganic materials, whiskers, wood pulps, and seeds of vegetables may be mentioned as exemplary. Among these, glass fibers or polytetrafluoroethylene particles, which are excellent in dispersibility in the viscose, are preferably dispersed in the spinning dope, and wood pulp or cut pieces of fibers are sometimes dispersed in the coagulation liquid. The spinning dope in the form of such a dis persion is introduced into the coagulation liquid to coagulate the same and is fibrillarly precipitated on the dispersed material to obtain a composite fibrous product in which the dispersed materials have been coated with fibril-like regenerated cellulose microfibers.

(3) The spinning apparatus is simple in structure and extremely high in productivity, and. the productivity thereof is increased by several tens of times, than in the case where a conventional nozzle is used.

(4) The fibrous product obtained by use of the spinning apparatus of the present invention is in a cut state and hence does not have to be subjected to a cutting operation.

(5) When the spinning apparatus of the present invention is connected with a paper-making machine, a nonwoven fabric can directly be obtained.

The fibrous product obtained according to the abovementioned process, which is composed of a large number of fibril-like microfibers, is ordinarily in a wet state. When desired to be used in a dry state, the fibrous product is preferably dried by solvent substitution, because it becomes a hard solid when dried.

Owing to its characteristics, the fibrous product of the present invention can be put into such uses as mentioned below.

The fibrous product is high in fibril-like structure and swellability, and hence can be used as fiber binders for papers and non-woven fabrics. Further, thermal fusibility can be imparted to the fiber binders. Such binding effects of the fibrous product are also successfully utilized, as well, when it is used as a reinforcing agent for concrete, mortar, gypsum and the other like construction materials. The fibrous product is high in porosity and large in surface area, and hence is useful as a heat insulator, an adsorbent and as a filter. The fibrous product is extremely high in water retainability and has properties similar to soil and, hence, can be used as materials for horticulture and artificial cultivation, and as improvers for sandy soil, volcanic ash soil, etc. The fibrous product is high in water retainability and slow in dehydration, and hence is used as a base material for fertilizers having a lasting eifect for forestry. Further, the fibrous product forms homogeneous aqueous slurries, and hence can be used as dust-preventing materials, base materials for cosmetics, etc.

The following examples are given merely as illustrative of the present invention and are not to be considered as limiting. Unless otherwise noted, the percentages therein and throughout the application are by weight.

EXAMPLE 1 A viscose containing 3.2% cellulose and 2.8% alkali and having a viscosity of poises was added without filtering and defoaming, at a rate of 400 cc./min. with vigorous stirring to an aqueous coagulation bath containing 80% acetone and 0.4% sulfuric acid and was kept at 20 C. A fibrousproduct (binder) having an apparent fiber length of -6 to 20 mm. was formed. This fibrous product was composed of a large number of fibril-like microfibers of about 0.2 to 2p in diameter.

The thus-obtained fibrous product was immersed for 2 minutes in an aqueous bath containing 0.5% sulfuric acid and kept at 50 C., washed with hot water at 60 C. and then scoured according to a conventional procedure. The fibrous product has a water swelling degree of 520% and a water retaining ratio of 3,300%. The fibrous product after scouring was defibrated, without drying, for 20 seconds in a mixer, charged into a dispersion of 3 denier viscose staple fibers of 6 mm. in length, and subjected to a paper-making operation. The amount of the fiber binder based on the weight of the viscose rayon fibers was 8%.

The physical properties of the thus-obtained paper are shown in Table 1.

A viscose containing 2% cellulose and 1.5% alkali and having a viscosity of 2 poises was added, without filtering and defoaming, to an aqueous coagulation bath containing 1.0% formaldehyde and 1.0% sulfuric acid,

by utilization of a reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of an aspirator-type spinning apparatus, to obtain a fibrous product composed of a large number of fibril-like microfibers having an average diameter of about 0.311..

The flow rate of the coagulation liquid at the narrowed portion of the spinning apparatus was 500 m./min.

The thus-obtained fibrous product wa's'scoured according to the conventional procedure, diluted with water to a cellulose concentration of 1%, defibrated for 30 seconds by means of a mixer, and then subjected to a freeness test by the use of a TAPPI type Canadian freeness tester, which indicated that the freeness thereof was 0.

The fibrous product had an apparent water swelling degree of 300% and a Water retaining ratio of 2,700%. This product was defibrilated, without drying, for 30 seconds by means of a mixer, added into a dispersion of 1.5 deniers viscose rayon fibers of 8 mm. in length, and subjected to a paper-making operation to obtain a nonwoven fabric which was not only strong but also excellent in hand.

EXAMPLE 3 Using an aspirator-type spinning apparatus, as in Example 2, a viscose containing 5% cellulose and 3% alkali and having a salt point of 9 and a viscosity of 30 poises was added, without filtering and defoaming, to an aqueous coagulation liquid at a high flow rate and containing 2% sulfuric acid and 3% sodium sulfate, thereby coagulating the viscose. At the same time, a shear stress was applied thereto, giving a form of fibril-like microfibers. Subsequently, the said flow was introduced into the second vapor ejector portion and passed as a fine flow of high speed.

The resulting fiber binder was scoured according to the conventional procedure.

The apparent fiber length of the thus-obtained fibrous binder was 3 to 28 mm. and the fiber fragment thereof Was composed of fine fibril-like regenerated cellulose microfibers of about 0.3 to 1.8,u. in diameter. The fibrous binder had an apparent swelling degree of 480% and a water retaining ratio of 3,000%.

This fiber binder was beaten in a pulp beater together with pulp, and the resulting mixture of pulp and the fiber binder was introduced into a dispersion of 3 denier commercial acrylic fibers of 8 mm. in length, formed into a web and dried to a non-woven fabric which was soft in hand.

The physical properties of the thus-obtained non-woven fabric are as shown in Table 2.

The same fibrous product after regeneration and scouring as in Example 2 was dried by means of solvent substitution using methanol and acetone. The dye exhaustion is shown in Table 3 (a) and for comparison, the dye exhaustion of a 3 denier ordinary rayon staple fiber of 51 mm. in length is shown in Table 3 (b).

TABLE 3 Dye exhaustion (percent):

EXAMPLE 5 A viscose containing 2% cellulose and 1.7% alkali and having a viscosity of 7 poises was added with a vinyl acetate-ethylene copolymer emulsion (Sumikaflex No. 500; trade name of Sumitomo Kagku Kogyo K.K.,

Japan) to prepare a spinning dope having a polymer concentration of 14%. The thus-prepared spinning dope was added to an aqueous coagulation bath containing 1% sulfuric acid and 70% methanol, by utilization of reduced pressure generated by flowing the coagulation liquid at the narrowed part at a high flow rate into the inner tube of an aspirator-type spinning apparatus, to obtain a fibrous product having a highly fibrillated structure. The flow rate of the coagulation liquid at the narrowed part of the spinning apparatus was 300 m./min. The fibrous product was composed of a combination of fibril-like regenerated cellulose microfibers with fibril-like vinyl acetate-ethylene copolymer.

This fibrous product was treated with an aqueous acid solution containing 2 g./1. of sulfuric acid and kept at 60 C., washed with water and then used as a fiber binder for the production of a non-woven fabric which was favorable in thermal fusibility andextremely high in wet strength.

EXAMPLE 6 Using an aspirator-type spinning apparatus, a viscose containing 4.5% cellulose and 3% alkali was added, without filtering and defoaming, into a high speed flow of a coagulation liquid containing 2% sulfuric acid and 1.5% sodium sulfate, by utilization of a reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of the spinning apparatus, to obtain a fibrous product composed of a large number of bril-like regenerated microfibers having an average diameter of 0.8g, which was then regenerated and scoured 7 according to the conventional procedures. The flow rate of the coagulation liquid at the narrow part of the spinning apparatus was 700 m./min.

. The thus-obtained fibrous product was diluted with water to a cellulose concentration of 1%, defibrated for 20 seconds by means of a mixer and then subjected to a freeness measurement by the use of a TAPPI type Canadian freeness tester, which indicated that the freeness thereof was 20.

The fibrous product was defibrated for 20 seconds by means of a mixer, dispersed in water, subjected to a papermaking operation by the use of a paper-making machine, without using a binder, disperser or the like, and then dried on a heated plate kept at 100 C. to obtain a paperlike construction high in strength.

The physical properties of the thus-obtained paper-like construction are as shown in Table 4.

The fibrous product (A) obtained in Example 5, the regenerated cellulose fibrous product (B) obtained in Example 6, and an acrylic fibrid (C) obtained according to the method disclosed in Japanese patent application No. 5,732/62 were compared with each other with respect to water retaining ratio and apparent swelling degree to obtain the results as set forth in Table 5.

TABLE Water Apparent retaining swelling ratio degree (percent) (percent) 10 EXAMPLE 8 A viscose containing 5.2% cellulose and 4.0% alkali was added at a rate of 1 liter/min. with vigorous stirring to a coagulation liquid containing 70% acetone and 0.5% sulfuric acid and kept at 10 C. to obtain a fibrous product having an apparent fiber length of 4 to 15 mm. This fibrous product was immersed for 1 minute in a bath containing 10 g./l. sulfuric acid and kept at 60 C., washed with hot water at 60 C. and then scoured according to the conventional procedure.

The thus-obtained fibrous product was composed of a large number of fibril-like regenerated cellulose microfibers of 0.6 to 2 in diameter and showed a swelling degree of 500% and a water retaining ratio of 3,000%.

This fibrous product was defibrated for 20 seconds by means of a mixer, dispersed in water and then subjected to a paper-making operation by the use of a paper-making machine, without using a binder or the like, to obtain a paper-like construction. The physical properties of the paper-like construction after drying are as shown in Table 6.

An ethylene-vinyl acetate copolymer (Flowback H 4011; trade name of Seitetsu Kagaku K. K., Japan) containing 20% vinyl acetate was dissolved in a 1:1 mixed solvent of benzene and dioxane to prepare a 10% solution.

On the other hand, a viscose containing 4.5% cellulose and 2.5% alkali was prepared. To this viscose, the abovementioned ethylene-vinyl acetate copolymer solution was added with vigorous stirring to prepare a spinning dope having a cellulose to copolymer ratio of 1:1. The thusprepared spinning dope was an emulsion of the copolymer in a viscose containing 2.7% cellulose and 1.5% alkali.

Using an aspirator-type spinning apparatus, the spinning dope was added, without filtering and defoaming, into a coagulation liquid containing 1.0 sulfuric acid, by utilization of a reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of the spinning apparatus, to obtain a fibrous product composed of a large number of fibril-like regenerated cellulose microfibers of 0.5 to 2p in diameter. This fibrous product was regenerated and scoured according to conventional procedures and then subjected to centrifugal dehydration. The obtained fibrous product had a swelling degree of 200% and a water retention ratio of 800%.

The thus-obtained fibrous product was defibrated for 30 seconds by means of a mixer, dispersed in water, subjected to a paper-making operation by the use of a papermaking machine, without using a binder, disperser or the like, dried and heat-treated on a metal plate at C. to obtain a non-woven fabric. The fabric was self-adherable and high in wet strength. The physical properties thereof are as shown in Table 7.

EXAMPLE A commercially available polyvinyl chloride was dissolved in a 1:1 mixed solvent of carbon disulfide and acetone to prepare a solution. This solution was added with vigorous stirring to water containing 150 p.p.m. of an anionic surface active agent to prepare an aqueous emulsion, which was then mixed with a viscose containing 6% cellulose and 4% alkali and having a salt point of 23 to prepare a spinning dope. The ratio of cellulose to polyvinyl chloride was 2: 1.

-The thus-prepared spinning dope was added, without filtering and defoaming, to a coagulation liquid containing 2.5% sulfuric acid and 1% formaldehyde with vigorous stirring to obtain a fibrous product composed of fibril-like microfibers of 0.3 to 0.9 in diameter. This fibrous product was regenerated and scoured according to the conventional procedures to show an apparent swelling degree of 400% and a water retaining ratio of 1,800%.

The fibrous product was defibrated for 3 minutes by means of a beater, dispersed in water and then subjected to a paper-making operation by the use of a paper-making machine, without using a binder. Subsequently, the web thus formed was dried and then heat-treated on a metal plate heated at 150 C. to obtain a paper-like construction which was not only excellent in self-bonding ability, but also high in wet strength.

The physical properties of the thus-obtained paper-like construction are as shown in Table 8.

A high pressure polyethylene for injection molding (Sumikasen G 806; trade name of Sumitomo Kagaku Kogyo K.K., Japan, was dissolved at an elevated temperature in a 1:1 mixed solvent of toluene and dioxane. The resulting solution, prior to formation of precipitate, was added with vigorous stirring to water containing 100 p.p.m. of a nom'onic surface active agent to prepare an emulsion. This emulsion was added into a viscose containing 2.7% cellulose and 1.8% alkali. The cellulose to polyethylene ratio in the viscose was 1:2.

The thus-prepared viscose was added with vigorous stirring to an aqueous solution containing 1% formaldehyde and 1% sulfuric acid to obtain a fiber binder having an apparent fiber length of 4 to mm. This fiber binder was composed of a large number of fibril-like microfibers of 0.2 to 15,41. in diameter.

The fibrous binder was treated with hot acidic water at 80 C. and then scoured according to an ordinary procedure. Subsequently, the binder was disintegrated for 20 seconds by means of a mixer, adding to a dispersion of viscose rayon fibers of 6 mm. x 4 d. and then subjected to a paper-making operation to obtain a fiber construction. The amount of the binder added was 20% based on the amount of the total fiber. The fiber construction was dried and fused on a hot plate at 130 C. The resulting nonwoven fabric-like construction was high in wet strength and had the tensile strength values shown in Table 9.

TABLE 9 Amount of binder percent 20 Weight g./m. 42 Dry strength kg./ 15 mm 2.05 Wet strength kg./ 15 mm 0.56 Apparent specific gravity g./cm. 0.25

EXAMPLE 12 A polyvinyl chloride having a polymerization degree of 2,000 was dissolved in a 1:2 mixed solvent of methylene chloride and tetrahydrofuran. The resulting solution was directly added with vigorous stirring to a viscose containing 5% cellulose and 3.5% alkali. The ratio of polyvinyl chloride to cellulose in the viscose was 1:1. The thusobtained viscose emulsion contained 3% of cellulose and 2.4% of alkali. Using an aspirator-type spinning apparatus, the viscose emulsion was added, without filtering and defoaming, to a coagulation liquid containing 2% of sulfuric acid by utilization of reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of the spinning apparatus, to obtain a fiber binder composed of a large number of fibril-like microfibers having an average diameter of 0.3a. The fiber binder had an apparent water swelling degree of 650%.

EXAMPLE 13 An ethylene-vinyl acetate copolymer (Evaflex 560 produced by Mitsui Polychemical K.K., Japan) c0ntaining 12% vinyl acetate was ground to less than mesh and added to a viscose containing 1.8% cellulose and 1.5% alkali. The ratio of copolymer to cellulose was 1:2. The resulting viscose was added, using the same aspirator-type spinning apparatus as in Example 2, an aqueous solution (coagulation liquid) containing 50% acetone and 0.5% sulfuric acid to obtain a fibrous binder.

The obtained fibrous binder was regenerated and scoured according to the conventional procedures, defibrated for 15 seconds by means of a mixer, added to a dispersion of viscose rayon fibers and then subjected to a paper-making operation. The amount of the binder was 18% based on the weight of the total fiber. The resulting paper-like material was dried on a hot plate at 150 C. to obtain a tough paper excellent in water resistance.

EXAMPLE 14 A viscose containing 8% cellulose and 5% alkali and having a salt point of 13 and a viscosity of 150 poises was added with 5 times the weight of the cellulose in the viscose of an aqueous ethylene-vinyl acetate copolymer emulsion Sumikaflex 400, trade name of Sumitomo Kagaku Kogyo K.K., Japan). The resulting mixture was diluted with water to prepare a spinning dope containing 1.2% cellulose, 6.0% of the copolymer and 0.75% alkali. This spinning dope was added at a rate of 100 cc./min. with vigorous stirring to a coagulation liquid prepared by adding 1% of sulfuric acid to a solution comprising 80% of methyl alcohol and 20% of water and was coagulated to obtain a fibrous product having an apparent fiber length of 2 to 25 mm. In the thus-obtained fibrous product, the copolymer component also had a fibril-like structure.

This fibrous product was defibrated for 25 seconds by means of a mixer to form a homogenous slurry composed of microfibers having a fiber length of less than 5 mm. The thus-formed slurry was added to an aqueous dispersion of the conventional 3 deniers acrylic fibers having a length of 5 mm. in an amount of 30% based on the weight of the acrylic fiber, subjected to a paper-making operation by the use of a cylinder paper machine and then dried on a Yankee drier having a surface temperature of C. to obtain a synthetic fiber paper. This paper was cut into two sheets, which were then superposed onto each other and treated with an iron at C., whereby the sheets were immediately bonded to each other.

EXAMPLE 15 A viscose containing 2.5% cellulose and 1.75% alkali was mixed, without filtering and defoaming, with 150%, based on the weight of the cellulose, of an aqueous dispersion of polytetrafluoroethylene powder (Teflon 30-J produced by Mitsui Fluorochemical K.K., Japan), followed by stirring, to prepare a dispersion. Using an 13 aspirator-type spinning apparatus, the thus-prepared dispersion was added to a coagulation liquid containing 1.0%

1 of sulfuric acid and 1.0% of formaldehyde by utilization of a reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of the spinning apparatus, to obtain a composite fibrous product of regenerated cellulose containing the polytetrafluoroethylene powder coated with the regenerated cellulose and having a fibril-like structure at the surface. The flow rate of the coagulation liquid at the narrowed portion of the spinning apparatus was 500 m./min. After scouring and bleaching, the thus-obtained fibrous product was whereby the regenerated cellulose was decomposed and a uniform polytetrafluoroethylene sheet was obtained.

EXAMPLE 16 A Kaolin (china clay) of about 200 mesh was dispersed in a coagulation liquid containing 3.0% sulfuric acid to prepare a 0.5% kaolin dispersion. In addition, a

viscose containing 4% cellulose and 2.5% alkali was prepared.

Using an aspirator-type spinning apparatus, the viscose was added to the kaolin-dispersed coagulation liquid by utilization of a reduced pressure generated by flowing the coagulation liquid into the inner tube of the spinning apparatus. The flow rate of the coagulation liquid at the narrowed portion of the spinning apparatus was 650 m./

' min. The ratio of the kaolin-dispersed coagulation liquid to the viscose was 8:1 by volume. The resulting material was a composite fibrous product comprising regenerated cellulose having the kaolin powder dispersed therein and having been partly fibrillated at the surface. The ratio of the kaolin to the regenerated cellulose in the product was 1.5:1 by weight.

EXAMPLE 17 A viscose containing 4% cellulose and 2% alkali and having a viscosity of poises was prepared. Into this viscose was dispersed, without beating, two times the weight of the cellulose in the viscose of a needle-leaved tree pulp which had been cooked according to the kraft method and then bleached.

Using an aspirator-type spinning apparatus, the thusobtained dispersion was added to an aqueous coagulation liquid containing 1.0% formaldehyde and 2.0% sulfuric acid, by utilization of a reduced pressure generated by flowing the said dispersion at a high flow rate of 600 m./ min. into the inner tube of the spinning apparatus. As a result, the short fibers of the pulp were bonded to each other by means of the regenerated cellulose microfibers and, at the same time, coated therewith to give a composite fibrous product which had been made longer in fiber length and partly fibrillated at the surface.

The fiber length of the wood pulp was 0.5 to 2 mm., while the apparent fiber length of the composite fibrous product was 2 to mm.

EXAMPLE 18 Dry flakes of cellulose diacetate were dispersed in a coagulation liquid containing 8.0% sulfuric acid to prepare a dispersion containing 0.5% of the flakes. On the other hand, a viscose containing 3.0% cellulose and 2.0% alkali was prepared. Using an aspirator-type spinning apparatus, the thus-prepared viscose was added to the abovementioned dispersion (coagulation liquid), by utilization of a reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of the spinning apparatus. The flow rate of the coagulation liquid at the narrowed portion of the spinning apparatus was 400 m./ min. As a result, the viscose was coagulated on the dispersed flakes to bond the flakes each to one another, thereby giving a, fibrous product in which the surfaces of the flakes were coated with the regenerated cellulose. The ratio of coagulation liquid to viscose was 8:1 by volume, and the fibrous product was composed of the regenerated cellulose and the flakes in a weight ratio of 3:4.

The composite fibrous product was uniformly dispersed in water, without separating and drying, and then subjected to a paper-making operation by the use of a Yankee machine to form a web and then dried. The dried web was extremely high in water resistance and was sufliciently resistant against bleaching and scouring.

Af-ter scouring, the paper layer was dried by means of a suction drum-type drier to obtain a non-woven fabric. The fabric was extremely tough and excellent in water retention, and had properties preferable for use as a diaper or the like article to be thrown away after use.

EXAMPLE 19 A viscose, containing 3.5% cellulose and 2.5% alkali was mixed with stirring with based on the weight of the cellulose, of copped glass :fiber strands (Asahi Fiber Flass CSC3HB) to prepare a spinning dope. Using an aspirator-type spinning apparatus, the thus-prepared spinning dope was added to a coagulation liquid containing 3.5 of sulfuric acid at a high flow rate, by utilization of a reduced pressure generated by flowing the coagulation liquid into the inner tube of the spinning apparatus, to obtain a composite fibrous product in which the glass fibers were coated with the regenerated cellulose and a part of the regenerated cellulose was brought into a fibril-like microfiber state. The flow rate of the coagulation liquid at the narrowed portion of the spinning ap paratus was 800 m./ min. The fibrous product was washed with water, bleached with an aqueous hypochloric acid solution, and then neutralized, washed with water and scoured.

The thus-treated fibrous product was dispersed in water, without using a binder or dispersant, and then subjected to a paper-making operation to obtain a paper-like prod uct which was tough due to self-adhesion of the fibers.

EXAMPLE 20 Into a coagulation liquid containing 1.0% sulfuric acid, cut acrylic fibers of 5 deniers and having a length of 5 mm., were dispersed to prepare a dispersion of 0.5% fiber content. In addition, a viscose containing 1.5% cellulose and 1.0% alkali was prepared by the conventional procedure.

Using an aspirator-type spinning apparatus, the thus prepared viscose was added to the above-mentioned dispersion (coagulation liquid), by utilization of a reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of the spinning apparatus to coagulate the viscose on the acrylic fibers. The flow rate of the coagulation liquid at the narrowed portion of the spinning apparatus was 600 m./min. Subsequently, the resultant product was introduced in the second stage ejector, and steam was flowed into the ejector to regenerate the cellulose. The ratio of the coagulation liquid to the viscose was 10:1.

The resulting composite fibrous product was immediately transferred onto a net to form a web, whereby a non-woven fabric excellent in strength and favorable in hand was obtained.

EXAMPLE 21 A viscose containing 3.0% cellulose and 2.0% alkali and having a viscosity of 6 poises was prepared. Using an aspirator-type spinning apparatus, the viscose was added without filtering and defoaming to a coagulation liquid containing 1.5% sulfuric acid and 0.7% formaldehyde, by utilization of a reduced pressure generated by flowing the coagulation liquid at a high flow rate into the inner tube of the spinning apparatus, to obtain a fibrous product comprising hydroxymethyl cellulose xanthate (reaction product of cellulose xanthate with formaldehyde). The flow rate of thecoagulation liquid at the narrow portion of the spinning apparatus was 900 m./min. The thus-obtained fibrous product, composed of a large number of fibril-like microfibers, had an apparent swelling degree of 620%, and a part of the fibrous product was in a dissolved state (solubility was 6%).

This fibrous product was subjected, without regeneration, to defibration for 20. seconds in a mixer, added to a dispersion of 3 deniers viscose ray fibers having a length of 6 mm. and then subjected to a paper-making operation. In this case, the dispersed fibers were formed into a web and, at the same time, were adhered to one another due to mutually entanglement of the said microfibers (first adhesion). Subsequently, the web comprising the unregenerated fibrous product was treated with a 1% aqueous sodium sulfate solution at 30 C. and having swellability for the unregenerated fibrous product to swell the said fiber material. At the same time, the web was subjected to an embossing treatment to reinforce the bonding of the fiber using an embossing roller having projections on the surface. Thereafter, the regeneration of the unregenerated fibrous product was completed by the use of an acidic bath kept at a high temperature, whereby the fibers constituting the web were mutually adhered (second adhesion).

The thus-treated web was subjected to washing with water, bleaching and drying to obtain a non-woven fabric which was soft and which was high in strength. The flow sheet of this example is shown in FIG. 5.

EXAMPLE 22 The fibrous product of Example 1 was dispersed in water to make a dispersion of weight percent solid concentration. The dispersion was treated as follows.

(A) 100 g. of the dispersion was poured in a polyethylene fiber sack, sealed after a thermometer was fixed at the center of the dispersion and then put in an ice-box to cool dOWn to about 4 C.

The cooled sack containing the dispersion was immersed into a water bath controlled at 40 C. to observe the change of the temperature of the dispersion.

(B) 100 g. of the dispersion was poured into a polyethylene film sack, sealed after a thermometer was fixed at the center of the dispersion and then heated in a boiling water bath for 20 minutes to make the temperature of the dispersion around 95 C.

The heated sack containing the dispersion was put into a cold water bath controlled at 15 C. to observe the change of the temperature of the dispersion.

As controls, distilled water and Icenon (trade name of a commercial material used for a head cooler pro- 1 6 duced by Kamata & Co. in Japan), were treated under the same conditions as in (A) and (B), respecti' ,vely.

The results are shown in FIGS. 6 and 7, wherein curve (a) is thefibrous product of the present invention, curve (f) is distilled water and curve (g) is the said commercial product Icenon. These curves show that the fibrous product of the present invention has superior thermal preserving properties as compared with those of the controls.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be apparent to those skilled in the art are intended to be included herein.

We claim:

1. A fibrous product comprising a large number of regenerated cellulose fibril-like microfibers having a diameter of 0.1 to 5 1 and a crystallization degree of less than 20%, at least a portion of said fibril-like microfibers being mutually entangled.

2. A fibrous product according to claim 1, which has a water-retaining ratio of 500 to 4,000% and an apparent swelling degree of to 800%.

3. A fibrous product comprising a large number of regenerated cellulose fibril-like microfibers having a diameter of 0.1 to 5 and a crystallization degree of less than 20%, and other material, at least a portion of said fibril-like microfibers being mutually entangled.

4. A fibrous product according to claim 3, wherein said other material comprises fibril-like microfibers of a synthetic polymer.

5. A fibrous product according to claim 3, wherein said other material comprises cut fibers.

6. A fibrous product according to claim 3, wherein said other material is in the form of granules.

7. A fibrous product according to claim 3, wherein said other material is in the form of flakes.

8. A fibrous product according to claim 4, wherein said synthetic polymer has a melting point of less than C.

9. A fibrous product according to claim 3, which has a water-retaining ratio of 300 to 2,000%.

References Cited UNITED STATES PATENTS 2,477,000 7/ 1949 Osborne 161-Microfiber 3,016,599 1/ 1962 Perry, Jr 161Microfiber 3,114,747 12/1963 Campbell 260-212 3,148,232 9/1964 Scheyer 264-108 WILLIAM J. VAN BALEN, Primary Examiner U.S. Cl. X.R. 

